Termination of optical fibers

ABSTRACT

An optical fiber connector has a housing including an axially extending passage with an exterior opening of first diameter and an interior opening of second diameter less than the first diameter and a frustro-conical wall bounding the passage and extending between the exterior and interior openings. The wall has an axial slot extending therethrough of axial extent equal to or less than the passage and extending axially across the interior opening. A separate biasing member may be included. The housing is thus equipped with selective radial expansibility for facilitating seating therein of an optical fiber plug having a frustro-conical exterior surface and an optical fiber centrally interiorly thereof.

FIELD OF THE INVENTION

This invention relates generally to optical fiber connection andpertains particularly to the termination of optical fibers supported inhousings molded thereon.

BACKGROUND OF THE INVENTION

In one present commercial optical fiber connection practice, an opticalfiber has a generally frustro-conical housing or plug applied thereto bymolding technique, and a receptor housing or sleeve is fabricated with afrusto-conical passage extending axially therein and adapted for receiptof the fiber so housed and for disposition of the fiber end face inregistry with an optic connection interface in the passage. The sleevedefines a companion such passage extending oppositely from the opticconnection interface, whereby the sleeve is adapted for receipt of asecond so housed fiber to connect two such fibers by disposing theirrespective end faces in registered contact at the sleeve connectioninterface. This optical fiber connection practice and apparatus thereofand connectors resulting therefrom are seen in a patent series includingU.S. Pat. No. 4,107,242 to P. K. Runge, U.S. Pat. No. 4,264,128 to W. C.Young, and U.S. Pat. No. 4,432,604 to R. E. Schwab, all such patentsbeing assigned to Bell Telephone Laboratories, Incorporated andincorporated herein by this reference thereto.

Single mode optical fiber connection practice, such as is attained bythe foregoing, imposes critical fiber end face relation as contrastedwith the lesser constraints of multimode optical fiber connection. Thus,in the single mode situation, no fiber end face spacing or separation istolerable, i.e., the end faces of two fibers being connected must be inmutual physical contact. Further, concentricity is paramount. In typicalinstance, the clad fiber may be one hundred and twenty five microns indiameter, with the fiber core at five microns diameter and coaxial withthe cladding. If the respective cores are misaligned concentrically bymore than one-half micron, the connection does not meet desired singlemode specifications and is to be rejected in quality control.

In the experience of the assignee of the present invention, in itslicensed practice under the above referenced patents, various factorshave been observed which lead to connectors produced and not within thenoted demanding specifications. Thus, given the close dimensionaltolerances as against such variables as mold matter density, curingtime, collective curing of products molded successively at differenttimes, temperature and humidity, etc., only selective ones of manyproduced connectors pass quality control. Typical rejection of productsat the quality control stage arises from dimensional mismatch as betweenthe sleeve frustro-conical surface and that of the fiber housing,whereby the end of the fiber housing so interferes with thefrustro-conical surface of the sleeve as to abut same and have its axialmovement arrested at a location spaced from the desired mutual contactinterface.

SUMMARY OF THE INVENTION

The present invention has as its primary object improved yield ofoptical fiber connectors of the above discussed type meeting thespecified single mode operational requirements.

A more particular object of the invention is the provision of sleevestructure which enhances fiber end face physical contact andfiber-to-fiber alignment.

The invention also looks to improved methods for optical fibertermination.

In attaining the foregoing and other objects, the invention introducesinto the sleeve set forth in the above-referenced patents an adaptivecapability for effecting disposition of fiber end faces precisely at thesleeve connection interface, despite the presence in the fiber housingand/or sleeve frustro-conical surfaces of out-of-tolerance dimensionswhich would give rise to quality control rejection of such connector ifit were to incorporate the sleeve structure of the referenced patents,i.e., in the absence of such adaptive capability. In compensating forsleeve material relaxation and the like with time and usage, theinvention includes biasing means for opposing such adaptive capability.

Such capability is achieved, in preferred practice and structure underthe invention, by rendering the sleeve selectively radially expansiblein its frustro-conical surface in manner permitting axial movement ofthe fiber housing in the sleeve, beyond that provided in the prior artsleeve, such that the fiber end face can be disposed at the sleeveconnection interface, despite such interference between the fiberhousing and sleeve frustro-conical surfaces as would preclude such endface disposition in the absence of such radial expansibility. The notedbiasing means is, in this instance, of type opposing radialexpansibility of the sleeve.

In the several embodiments below discussed, the sleeve radialexpansibility is provided by introducing a discontinuity in thefrustro-conical surface of the sleeve. Such discontinuity may be in theform of a slot extending partially axially of the sleeve, opening intothe frustro-conical surface and encompassing the sleeve connectioninterface. In this instance, the biasing means will comprise sleevecontinuous portions adjacent the slot. The slot may also extend fullyaxially of the sleeve, in which case, the biasing means may bestructurally distinct from the sleeve and disposed either within orexternal to the sleeve for applying radially inwardly directed force tothe sleeve. Such separate biasing means may also be employed with thepartially extending slot.

The foregoing and other objects and features of the invention will befurther understood from the following detailed description of preferredembodiments and practices and from the drawings, wherein like referencenumerals identify like parts throughout.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a central sectional view of the prior art sleeve with left andright fiber plugs spaced from the sleeve along the sleeve axis.

FIG. 2 is a reduced scale elevation of the sleeve of FIG. 1 as would beseen from plane II--II of FIG. 1.

FIG. 3 is a reduced scale elevation of the right fiber plug of FIG. 1 aswould be seen from plane III--III of FIG. 1.

FIG. 4 is an enlarged schematic showing of FIG. 1 with a dimensionallyout-of-tolerance left fiber plug and a dimensionally in-tolerance rightfiber plug seated in the sleeve.

FIG. 5 is a central sectional view of a sleeve structure having a fullyextending slot without separate bias as would be seen from plane V--V ofFIG. 6.

FIG. 6 is an elevation of the sleeve of FIG. 5 as would be seen fromplane VI--VI of FIG. 5.

FIG. 7 is an enlarged schematic showing of the FIG. 1 right and leftfiber plugs during transition seating thereof in the sleeve of FIG. 5.

FIG. 8 is an enlarged schematic showing of the FIG. 1 right and leftfiber plugs upon full seating thereof in the sleeve of FIG. 5.

FIG. 9 is a central sectional view of a first sleeve structure inaccordance with the present invention as would be seen from plane IX--IXof FIG. 10.

FIG. 10 is an elevation of the sleeve of FIG. 9 as would be seen fromplane X--X of FIG. 9.

FIG. 11 is a central sectional view of a second sleeve structure inaccordance with the present invention as would be seen from plane XI--XIof FIG. 12.

FIG. 12 is a sectional elevation of the sleeve of FIG. 11 as would beseen from interior plane XII--XII of FIG. 11.

FIG. 13 is a central sectional view of a third sleeve structure inaccordance with the present invention as would be seen from planeXIII--XIII of FIG. 14.

FIG. 14 is a sectional elevation of the sleeve of FIG. 13 as would beseen from interior plane XIV--XIV of FIG. 13.

FIG. 15 is a central sectional view of a fourth sleeve structure inaccordance with the present invention.

FIG. 16 is a central sectional view of a fifth sleeve structure inaccordance with the present invention.

FIG. 17 is a central sectional view of an optical fiber-to-transducertermination device in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS AND PRACTICES

Referring to FIGS. 1-3, optical fiber connector 10 of the prior artreferred to above includes sleeve 12 having leftward and rightwardopenings 14 and 16 of first diameter into axial passage 18. Passage 18includes a leftward portion 20 bounded by frustro-conical surface 22 anda rightward portion 24 bounded by frustro-conical surface 26. Surfaces22 and 26 intersect at interior opening 28 of sleeve 12, same being ofsecond diameter which is less than the first diameter, i.e., of exterioropenings 14 and 16, and constitutes a fiber connection interface. Sleeve12 is typically a molded plastic body.

Leftward fiber plug 30 includes a plastic housing 32 molded aboutoptical fiber 34. Housing 32 has frustro-conical surface 36 extendingbetween its location 38 and plug end 40, respectively of theabove-mentioned first and second diameters.

Rightward fiber plug 42 includes a plastic housing 44 molded aboutoptical fiber 46. Housing 44 has frustro-conical surface 48 extendingbetween its location 50 and plug end 52, respectively of theabove-mentioned first and second diameters.

The first called-out diameter, that of openings 14 and 16 and oflocations 38 and 50 of plugs 30 and 42, is greater than the secondcalled-out diameter, that of opening 28 and of ends 40 and 52 of plugs30 and 42.

Turning to FIG. 4, plug 53 is depicted with an out-of-tolerance housing,not residing in sleeve frustro-conical surface as per specifications.Thus, frustro-conical surface 54 of plug 53 is configured such that itslarger end 56 so interferes with surface 22 that margin 58a of end 58cuts or digs into surface 22, arresting movement of end 58 into registrywith sleve interface 28.

The prior art connector of FIG. 4 is out-of-specification clearly sincephysical contact does not occur as between ends 58 and 66 of plugs 53and 60 and fibers 68 and 70 are not mutually concentrically registeredalong sleeve axis 72.

For correction of the situation applying in FIG. 4, sleeve 74 of FIGS. 5and 6 includes first exterior openings 76 and 78 into axial passage 80,having leftward portion 82 bounded by frustro-conical surface 84 andrightward portion 86 bounded by frustro-conical surface 88. Surfaces 84and 88 jointly define axial discontinuity 90, extending fully alongsleeve 74 axis 92, and encompassing interface 94 of sleeve 74, which iscoextensive with the interior ends of sleeve portions 82 and 86 and ofthe second smaller aforementioned diameter. As will presently bediscussed, discontinuity 90 provides sleeve 74 with a capability forradial expansibility for registration of out-of tolerance plug 53 withits sleeve housing portion.

Referring to FIG. 7, as margin 58a of smaller end 58 of plug 53confronts frustro-conical surface 84, discontinuity 90 facilitates aradial distension of sleeve 74 adjacent interface 94, whereby margin 58adoes not interfere with surface 84, in contrast to its interference withsurface 22 as above discussed. The diameter dimension of interface 94 istransitionally enlarged from diameter D to diameter D1, corresponding tothe distance D2 by which the interface need be enlarged to avoid suchinterfering fit as shown in FIG. 4. Discontinuity 90 thus increasestransitionally in extent from E to E1.

Following the transitional shape change of sleeve 74 shown in FIG. 7,the situation matures to that shown in FIG. 8, i.e., end face 58 mergeswith interface 94 and discontinuity 90 returns, under natural constraintof its parent body, to extent E.

The sleeve of FIGS. 5 and 6, i.e., of type having a fully axiallyextending discontinuity without external bias, which evolved in thecourse of reaching the present invention, is not the subject of thispatent application, the invention and is not claimed herein. Theforegoing discussion of radial expansion and registration ofout-of-tolerance will, however, be seen to have like applicability toconnectors and housings of the invention.

Turning now to FIGS. 9 and 10, a first version of structure inaccordance with the invention comprises sleeve 96, having only a limiteddiscontinuity 99 in its frustro-conical surfaces 98 and 100, havingcourse encompassing connection interface 102 but not extending fullyaxially of passage 104. Thus, radial extension of passage 104 isacceptable, for purposes of the invention, if same provides fordistension of passage 104 encompassing interface 102 sufficient toaccomodate full axial movement of inserted plugs to interface 102. Aswill be seen, surfaces 98 and 100 have extents radially and axiallysuccessive to discontinuity 99 which are continuous and solid, asmolded, and which provide, in effect, a self-bias within sleeve 96,applying radially inwardly directed force in opposition to such radialexpansion of passage 104 adjacent interface 102, such force being ofgreater measure than exists in the case of the fully axially extendingslot of FIGS. 5 and 6.

In the embodiment of the invention shown in FIGS. 11 and 12, sleeve 106is shown with fully axially extending discontinuity 108 and embodies aC-shaped biasing means inthe form of spring 110, generally encompassinginterface 112 of sleeve 106 to impose on sleeve 106 a radial interiorlydirected force adapted to reinstate the dimension of discontinuity 108after sleeve radial expansion, despite age relaxation of the material ofsleeve 106. Discontinuity 108 may be fully axial in extent with passage114, as shown, or of limited axial extent encompassing only interface112.

In the further embodiment of the invention shown in FIGS. 13 and 14,sleeve 116 has a radially extending centrally situated recess 118 forreceipt of spring 120, shown in the form of a C-shaped member,insertable into recess 118, again for imposing external and independentradial constraint on the sleeve passage and discontinuity 122, hereshown as being full axial extent.

In FIG. 15, sleeve 124 is configured as in the case of the sleeve ofFIGS. 11 and 12, i.e., integrally molded with a biasing means. Here,sleeve 124 includes C-shaped spring 126 having radially exteriorlyextending members 128 and 130, mutually axially spaced, and radiallyinteriorly extending member 132, which serve during molding tointimately anchor the parts of the molded assembly and to enhancecoaction of the sleeve and the spring during use.

Turning to FIG. 16, sleeve 134 is likewise configured as in the case ofthe sleeve of FIGS. 11 and 12, i.e., also integrally molded with abiasing means. Here, sleeve 134 includes C-shaped spring 136 havingradially interiorly extending members 138, 140 and 142, mutually axiallyspaced and serving function akin to anchoring members 128, 130 and 132above discussed.

FIG. 17 illustrates a still further embodiment of the invention, whereinhousing 143 has passage 144 with but a single portion 146, terminatingat interface 148 and bounded by frustro-conical surface 150.Discontinuity 152 extends partially axially with passage 144, interiorlyof its open end as shown. Housing 143 supports therein an active opticalfiber terminator 154, e.g., a light-sensitive transducer, in contrast tothe fiber-to-fiber termination of the previously discussed devices.Transducer 154 is aligned by housing 143 precisely with central axis 156and the housing may define a channel 162 for passage of conductors 158and 160 of transducer 154 to user apparatus, not shown. A fiber plug,such as plug 30 of FIG. 1 is introduced in passage 144 and isaccomodated, by discontinuity 152 for full passage into registry withinterface 148 to precisely register with transducer 154.

While radial expansibility of sleeves having one or more interiorfrustro-conical surfaces has been illustrated particularly bydiscontinuities therein, it may be more broadly observed that theinvention encompasses diverse radially and axially successive extentsadjacent the optical fiber connection interface, i.e., the smallerinterior end of the frustro-conical surface. Viewing FIG. 9, one suchextent is defined by slot 99, which is an open sleeve portion, andanother such extent is defined by the presence of sleeve surfaceradially and axially continuous with the slot. Clearly, one maysufficiently weaken the sleeve selectively in the vicinity of theconnection interface to achieve such radial expansion as required toprovide full plug movement axially to the sleeve connection interface.

As will be seen, the invention provides optical fiber connector housing,optical fiber connectors and methods for optical fiber termination inits various aspects, as set forth in the ensuing claims. Various changesin structure and modifications in methodology may be introduced withoutdeparting from the invention. Accordingly, it will be understood thatthe particularly depicted embodiments and practices are intended in anillustrative and not in a limiting sense. The true spirit and scope ofthe invention is set forth in the following claims.

I claim:
 1. An optical fiber connector comprising a housing having anaxially extending passage with a first exterior opening of firstdiameter and a second interior opening of second diameter less than saidfirst diameter and a frustro-conical wall bounding said passage, saidwall having diverse radially and axially successive extents adjacentsaid second opening and therey having selective radial expansibility forfacilitating seating of an optical fiber plug therein.
 2. The connectorclaimed in claim 1 further including separate biasing means for opposingradial expansibility of said housing.
 3. The connector claimed in claim2 wherein said biasing means is disposed fully within said housing inpartly encircling relation to said passage.
 4. The connector claimed inclaim 3 wherein said housing comprises a plastic body molded about saidbiasing means.
 5. The connector claimed in claim 2 wherein said biasingmeans is disposed upon an exterior surface of said housing in partlyencircling relation to said passage.
 6. The connector claimed in claim 5including a radially recessed portion bounded by said exterior surfaceupon which said biasing means is disposed.
 7. The connector claimed inclaim 1 wherein one of said diverse extents of said wall comprises aslot extending through said wall, the others of said diverse extentscomprising sleeve portions continuous with said slot.
 8. The connectorclaimed in claim 7 wherein said slot extends from said second opening toa location distal from said first opening.
 9. An optical fiber connectorcomprising a housing having an axially extending passage with a firstexterior opening of first diameter and a second interior opening ofsecond diameter less than said first diameter and a frustro-conical wallbounding said passage, a plug having an end of said second diameter anda frustro-conical surface extending from said plug end to anintermediate location in said plug of said first diameter, said plugcontaining therein an optical fiber with a fiber end face registeredcentrally with said plug end, said wall having diverse radially andaxially successive extents adjacent said second opening and therebyhaving selective radial expansibility for facilitating seating of saidplug.
 10. The connector claimed in claim 9 further including separatebiasing means for opposing radial expansibility of said housing.
 11. Theconnector claimed in claim 10 wherein said biasing means is disposedfully within said housing in partly encircling relation to said passage.12. The connector claimed in claim 11 wherein said housing comprises aplastic body molded about said biasing means.
 13. The connector claimedin claim 10 wherein said biasing means is disposed upon an exteriorsurface of said housing in partly encircling relation to said passage.14. The connector claimed in claim 13 including a radially recessedportion bounded by said exterior surface upon which said biasing meansis disposed.
 15. The connector claimed in claim 9 wherein one of saiddiverse radial and axial extents of said wall comprises a slot extendingthrough said wall, the others of said diverse radial and axial extentscomprising sleeve portions continuous with said slot.
 16. The connectorclaimed in claim 15 wherein said slot extends from said second openingto a location distal from said first opening.
 17. An optical fiberconnector housing having an axially extending passage with a firstexterior opening of first diameter, a second interior opening of seconddiameter less than said first diameter and a third exterior opening ofsaid first diameter, and a pair of frustro-conical walls bounding saidpassage and extending respectively from said first opening to saidsecond opening and from said third opening to said second opening, eachof said walls having diverse radially and axially successive extentsadjacent said second opening and thereby having selective radialexpansibility for facilitating seating of an optical fiber plug therein.18. The housing claimed in claim 17 further including separate biasingmeans for opposing radial expansibility of said housing.
 19. The housingclaimed in claim 18 wherein said biasing means is disposed fully withinsaid housing in partly encircling relation to said passage.
 20. Thehousing claimed in claim 19 wherein said housing comprises a plasticbody molded about said biasing means.
 21. The housing claimed in claim18 wherein said biasing means is disposed upon an exterior surface ofsaid housing in partly encircling relation to said passage.
 22. Thehousing claimed in claim 21 including a radially recessed portionbounded by said exterior surface upon which said biasing means isdisposed.
 23. The housing claimed in claim 17 wherein one of saiddiverse radial and axial extents of each said wall comprises a slotextending through said wall, the others of said diverse radial and axialextents comprising sleeve portions continuous with said slot.
 24. Thehousing claimed in claim 23 wherein said slot extends from said secondopening to locations respectively distal from said first and thirdopenings.
 25. An optical fiber connector comprising a housing having anaxially extending passage with a first exterior opening of firstdiameter, a second interior opening of second diameter less than saidfirst diameter and a third exterior opening of said first diameter, anda pair of frustro-conical walls bounding said passage and extendingrespectively from said first opening to said second opening and fromsaid third opening to said second opening, and a pair of plugs, eachplug having an end of said second diameter and a frustro-conical surfaceextending from said plug end to an intermediate location in said plug ofsaid first diameter, each said plug containing therein an optical fiberwith a fiber end face registered centrally with said plug end, each saidwall having diverse radially and axially successive extents adjacentsaid second opening and thereby having selective radial expansibilityfor facilitating seating of said plugs.
 26. An optical fiber connectorcomprising a housing having an axially extending passage with a firstexterior opening of first diameter and a second interior opening ofsecond diameter less than said first diameter and a frustro-conical wallbounding said passage, said wall having an opening extending fullyaxially thereof and thereby having selective radial expansibility forfacilitating seating of an optical fiber plug therein, and separateresilient biasing means for opposing radial expansibility of saidhousing, said resilient biasing means being in generally encirclingrelation to said passage and in registry with said second diameteropening thereof.
 27. The connector claimed in claim 26 wherein saidbiasing means is disposed fully within said housing.
 28. The connectorclaimed in claim 27 wherein said housing comprises a plastic body moldedabout said biasing means.
 29. The connector claimed in claim 26 whereinsaid biasing means is disposed upon an exterior surface of said housing.30. The connector claimed in claim 29 including a radially recessedportion bounded by said exterior surface upon which said biasing meansis disposed.
 31. A method for optical fiber termination, comprising thesteps of:(a) supporting an optical fiber in a housing and defining afrustro-conical exterior surface for said fiber housing having an endwith which said fiber has an end face in registry; (b) defining areceptor housing for said fiber housiing having an opening for receiptof said fiber housing and a fiber termination interface with afrustro-conical interior surface extending from said opening to saidinterface; (c) working said receptor housing frustro-conical surface toprovide said housing with a capacity for radial expansion sufficient topermit full axial movement of said fiber housing end to register withsaid receptor housing interface despite configurational disparitiesbetween said exterior and interior frustro-conical surfaces; and (d)effecting generally encircling radial bias to said receptor housing inopposition to such radial expansion thereof by applying a resilientmember thereto.
 32. The method claimed in claim 31 wherein said step (c)is practiced by forming a slot extending axially with said receptorhousing and through said interior frustro-conical surface.
 33. Themethod claimed in claim 32 wherein said step (c) is practiced by formingsaid slot fully axially coextensive with said receptor housing.
 34. Themethod claimed in claim 32 wherein said step (c) is practiced by formingsaid slot through said interface with a slot end distal from saidreceptor housing opening.